Dyson’s Long Shot

Dyson’s Long Shot

Freeman Dyson is betting that alien life doesn’t live on a world like yours. More specifically, if you check out the tentative wager this celebrated physicist has logged at the Web site www.longbets.org, you’ll see that Dyson’s hunch is that the first discovery of extraterrestrial life will be made someplace other than on a planet or on a satellite of a planet.

In other words, if we succeed in finding some biology beyond Earth, it won’t be camped out on a large ball of rock.

I have great admiration for Freeman Dyson’s breathtaking ideas. But I suspect he’s taking a long shot here. He hasn’t qualified the bet to say "intelligent extraterrestrial life."

So if an upcoming mission to Mars, Titan, or Europa discovers microbes busy eking out a living deep underground or afloat in hidden oceans of water or natural gas, then Dyson will have to pay up, assuming we haven’t found some other biology first.

Is there something else we could find first?

There’s always the possibility of breaking open a fallen meteorite to reveal some sort of metabolizing slime within. Or maybe intelligent aliens will make an unequivocal landing behind the White House rose garden. But if you’re talking near-term success in uncovering life elsewhere, then SETI’s a big part of the mix. SETI, of course, could find a signal at any time.

So how reasonable is Dyson’s hypothesis of a non-planetary home for intelligent life? After all, the usual convention in SETI – as expressed in everything from the Drake Equation to the strategy of targeted searches – is that complex, thinking beings will evolve on Earth-like worlds, and stay there.

The first conjecture isn’t enormously controversial. But the second may be too conservative. Intelligent beings might travel, and at the very least could spread through their own solar systems. Dyson has pointed out that the fundamental problem with planets is that there’s not much real estate for the mass involved.

Spheres have the minimum surface area for a given volume of stuff. You can improve things by chopping the Earth in two and rolling up each of the halves like clay balls. This will increase the acreage by 26%. Do it again (now four balls), and you’ll win another 26%.

Reconfiguring Earth is a big job, and would probably run afoul of environmental protection agencies. But there’s no need: as Dyson has noted, if more space is your thing, then the asteroids are already available as bite-size hunks of matter, close enough to the Sun to intercept interesting amounts of energy, and composed of materials suitable for supporting life. There’s at least ten thousand times as much surface area on the asteroids as on our home planet. So our future, Dyson suggests, lies in exploiting this abundant acreage, for otherwise we may crowd ourselves into a nasty situation here on Earth.

Assuming that intelligent species elsewhere have done the same, shouldn’t we be broadening (in a literal sense) our SETI searches?

In fact, our searches already are broad! The Arecibo telescope’s beam, as used for Project Phoenix, covers all of a 100 light-year-distant solar system out to two thousand times the Earth-Sun distance. It will encompass anyone’s asteroid belt. Our optical searches are similarly sensitive to wide swaths of other star systems.

But what if life has adapted to existence in a vacuum (another Dyson suggestion)? You might think that life in a vacuum sucks, but if such atmosphere-independent biology exists, it might migrate to giant molecular clouds and other interstellar feeding grounds where resources are far more plentiful than in a planetary system. If this has happened, SETI sky surveys (such as SERENDIP IV, the data-collecting component of the SETI@home effort) might turn up intelligence situated between the stars.

Is Freeman Dyson right?

Obviously, no one yet knows, and it’s certainly possible that life – even of the savvy variety – might be situated elsewhere than on planetary surfaces. Fortunately, today’s SETI searches have those extraplanetary bases reasonably covered.

Meanwhile, those who are optimistic about the chances for finding life beneath Mars’ dusty dirt or under Europa’s icy crust may wish to step forward and take up Freeman Dyson’s bet.